This device is designed for a particular type of paper towel holder that we use for toilet rolls in our office. It has an 8mm square rod in a "U" shape hanging sideways from a protruding wall fixture. when two rolls are placed on it, and one roll is pulled, both rolls spin - this is designed to prevent the friction from the first roll, from unrolling the second. However - I'm sure you will find many more useful applications for this round disc with a square hole - such as adapting a square leg into a round hole, or as a dummy i-chin coin.